Paper making system and apparatus

ABSTRACT

This invention relates to the control of the viscosity of the water in a traveling sheet or web as it advances through a manufacturing operation as in a paper making process. For example, microwave energy can be applied to the water wet web to raise the temperature of the water in the traveling web and so reduce the viscosity of the water. Thereafter the web is passed through a press section which reduces the water content of the web. If reduction in the water content of the web is not required, then the web can be cooled to increase the viscosity of the water so less water is removed in the press section. Preferably and in accordance with this invention, application of the microwave energy or cooling of the web is selectively effected in a plurality of zones, the total width of the zones covering the width of the traveling web. Moisture measuring means are provided downstream from the press section to determine the moisture content in each of the several zones across the width of the traveling web. This means emit signals which are applied to controllers relating to the output of each waveguide means and each cooling means in the several zones across the width of the sheet to change the output of each of the waveguide means or each of the cooling means to the sheet proper. In this manner, it is possible to effect more uniform drying of the sheet for the tendency is for the edges of the sheet to dry more readily than the middle portion of the sheet.

United States Patent Goerz, Jr. et al.

[54] PAPER MAKING SYSTEM AND APPARATUS [721 lnvenmm Yi. 1:. 99 JFLMFFM? P rks. Erik W- Stephansen, Foster City, both of Calif.

[73] Assignee: Bechtel International Corporation 22 Filed: Dec. 16, 1970 7 [211 App]. No.: 98,685

Primary Examiner-Carroll B. Dority, .lr. Attorney-Eckhoff and Hoppe 1 July 25, 1972 [5 7] ABSTRACT This invention relates to the control of the viscosity of the water in a traveling sheet or web as it advances through a manufacturing operation as in a paper making process. For example, microwave energy can be applied to the water wet web to raise the temperature of the water in the traveling web and so reduce the viscosity of the water. Thereafter the web is passed through a press section which reduces the water content of the web. If reduction in the water content of the web is not required, then the web can be cooled to increase the viscosity of the water so less water is removed in the press section. Preferably and in accordance with this invention, application of the microwave energy or cooling of the web is selectively effected in a plurality of zones, the total width of the zones covering the width of the traveling web. Moisture measuring means are provided downstream from the press section to determine the moisture content in each of the several zones across the width of the traveling web. This means emit signals which are applied to controllers relating to the output of each waveguide means and each cooling means in the several zones across the width of the sheet to change the output of each of the waveguide means or each of the cooling means to the sheet proper. In this manner, it is possible to efiect more uniform drying of the sheet for the tendency is for the edges of the sheet to dry more readily than the middle portion of the sheet.

3 Claims, 5 Drawing Figures PATENYEDJIILZS I972 SHEET 1 OF 2 In in mm W 3 0 vb M INVENTORS DAVID J. 605/22 JR. BY ERIK w. STEPHANSEN 940.

-- ATTORNE Y5 PATENTEOJuL25 I972 SHEET 2 BF 2 l I I I INVENTORS DAVID J. GOERZ, JR. RIK W. STEPHANSEN ATTORNEYS 1 PAPER MAKING SYSTEM AND APPARATUS BACKGROUND OF THE INVENTION In the manufacture of paper, a slurry of the paper pulp in water is applied to a continuously moving forming wire. Water forms the major component of the slurry, providing about 99 k percent of the slurry. The removal of this large quantity of water from the slurry is an essential and expensive portion of the paper making operation. Various methods of removing the water from the web have been employed in the past, such as open flame heaters, heating the entire mass of the stock in the head box before it is applied to the forming wire, applying steam showers to the surface of the stock as it passes the suction boxes, couch roll or the press section; or using infra red, gas or electric heaters. Each of these is subject to various objections. For example, infra red and electric heaters as well as open flame heaters have the disadvantage in that they can supply only a certain amount of heat to the stock or to the web since the web itself acts as a heat insulator. The result is that only the outer surfaces of the web are heated sufficiently to vaporize moisture therefrom while the interior of the stock remains at a relatively low temperature.

In accordance with this invention, heating or cooling energy is applied selectively to each of the plurality of zones across the'traveling sheet or web in or ahead of the press section. The effect of this energy application is to decrease or increase the temperature of the water and so alter the viscosity of the water in a given zone so that the press section is effective to remove the required amount of water from a given zone. As a result, the press section is made much more efficient in its removal of water from the sheet or web. Further and in accordance with this invention, the microwave energy and the cooling energy are each applied in parallel zones across the traveling web. The application of the microwave energy and the cooling energy is under the control of a control device which regulates the amount of microwave energy and cooling energy applied in a given zone. The control is in turn operated in accordance with instructions received from a control device such as a computer and operated by moisture detecting means downstream from the press section. This means extends across the web to detect the amount of moisture present and coordinate the application of microwave energy or cooling energy in a given zone with the need for a decrease or an increase in application of each such energy to achieve the requisite moisture removal. For a more detailed discussion of a suitable structure for applying microwave energy in parallel zones to a moving web of material and for means for controlling the generation of microwave energy in each of the zones, see U.S. Pat. No. 3,470,343. The tendency is for the edges of the sheet to dry more readily than the middle portion and hence the edges do not require as much microwave energy application as the middle portion of the sheet.

SUMMARY OF THE INVENTION It is in general the broad object of the present invention to provide an improved high speed paper making system and method for drying of a paper stock.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic layout of an apparatus setup for practicing the present invention on a paper machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIG. 1, this shows a paper making machine setup embodying the present invention and which includes a Fourdrinier section, designated generally at 10. A head box 11 supplies a slurry of paper pulp to the forming wire 12. The head box 11 is provided with a slice 16 which delivers a slurry of about one-half percent consistency and about 99 A: percent water. The slurry passes through the Fourdrinier section 10 to form a web on the wire which is subsequently delivered to a press section which includes press rolls I3 and 14. As the slurry is carried by the forming wire, a portion of the water associated with the slurry is seperated therefrom and passes through the forming wire 12. The removal of water on the wire is effected by the use of so-called table rolls, foils or suction boxes. Further water removal is effected by a first set of press rolls l3 and 14. In the press section, the web is subjected to a dual source of microwave energy and of cooling energy, generally indicated at 17, which dual source extends across the web.

The source of microwave energy 17 feeds waveguide 18 which will be hereinafter described in detail. The source of microwave energy can be any well-known source, such as shown in US. Pat. No. 3,470,343, and in one practical embodiment of the invention we employed a klystron and associated power supply operating at 2,450 mHz. Suitably, the RF generator operates at a frequency from about 300 to 30,000 mHz. Thus, the ISM allocated frequencies of 915, 2,450, 5,800 and 22,125 mHZ are suitable.

Following the application of the required microwave energy or cooling energy of the web, the web is passed through a second set of press rolls 19 and 21. The effect of application of the microwave energy is to heat the water present selectively and raise its temperature and so it reduces its viscosity, thus increasing the removal of water from the web which is unaffected by the application of microwave energy. The waveguide may be provided with a dummy load, not shown, to absorb excess energy and, in case of a web break, to absorb total energy input. The cooling energy application lowers the viscosity of the water in the zone of its application and so reduces the amount removed in the press section. The cooling energy can be applied by any well-known means.

The waveguide described hereinafter in detail is split and power is introduced to the structure on both sides of the web, as appears in FIG. 3, where is shown a plurality of spaced parallel side walls 22 extending downwardly from the energy source 17 to direct the microwave energy to both sides of the web. The side walls 22 can be extended in the direction of the run of the web or can be at an angle thereto as appears in FIG. 5.

Following passage through the press rolls 19 and 21, the web passes through a main dryer section 23 and thence through a size press 24 and thence to an after dryer section 26 and finally to a collection roll 30. After the web issues from the after dryer section, it passes through a sensing mechanism, generally indicated at 27, which extends across the web. The sensing mechanism may include a plurality of spaced moisture detention devices which sense or scan the moisture content in different spaced areas across the web. We prefer a single sensing or scanning device which moves back and forth across the web, detennining the water content of the web as it traverses the web. The information so ascertained is fed back through the line, generally indicated at 28, to control mechanism 29 which in turn through line 31 controls the application of both the microwave energy and the cooling energy to the respective segments of the web. This is highly desirable inasmuch as the tendency is for the web to dry more quickly at the edges than in the area adjacent to and at the center of the web whereby less microwave energy application is required at the edges than in the center and where cooling may be called for. This enables a more uniform moisture content to be readily obtained. The sensing mechanism and the control mechanism are each well-known in the art, as exemplified in US. Pat. No. 3,470,343, for example, and are not therefore described in detail and one can refer to the presently known art.

We claim:

l. A method of drying paper stock in the form of a traveling web containing water comprising applying microwave energy in a plurality of zones extending transversely across the web to heat the water to decrease the viscosity of the water, then pressing the web to remove water therefrom, measuring the moisture content of each of said zones following water removal, and selectively controlling the application of microwave energy in each of said zones in response to the measurement of the moisture content in each of said zones.

2. Apparatus for the heat treatment of traveling sheet and web materials comprising microwave guide means having slots along opposed walls of a microwave energy path therethrough, said slots being adapted for the passage of the width of the traveling sheet or web of material across said path, each slot applying microwave energy to a pre-selected portion of the width of the material to heat the water therein and so reduce its viscosity, a press section for removing the heated water from the material, detector means to measure the moisture content of said material after passage through said energy path and the press section and transmit a signal indicator of the water content of the web, respective controllers connected one to each slot to control the microwave energy output therefrom, and means applying to said controllers the signals emitted by said detector means to relate the output of each waveguide means to the water content measurement of a corresponding portion of the width of the material.

3. A method of drying paper stock in the form ofa traveling web containing water comprising selectively applying microwave energy in each of a plurality of zones extending transversely across the web to alter the viscosity of the water, then pressing the web to remove water therefrom, measuring the moisture content of each of said zones following water removal, and selectively controlling the application of the microwave energy in each of said zones in response to the measurement of the moisture content in each of said zones. 

1. A method of drying paper stock in the form of a traveling web containing water comprising applying microwave energy in a plurality of zones extending transversely across the web to heat the water to decrease the viscosity of the water, then pressing the web to remove water therefrom, measuring the moisture content of each of said zones following water removal, and selectively controlling the application of microwave energy in each of said zones in response to the measurement of the moisture content in each of said zones.
 2. Apparatus for the heat treatment of traveling sheet and web materials comprising microwave guide means having slots along opposed walls of a microwave energy path therethrough, said slots being adapted for the passage of the width of the traveling sheet or web of material across said path, each slot applying microwave energy to a pre-selected portion of the width of the material to heat the water therein and so reduce its viscosity, a press section for removing the heated water from the material, detector means to measure the moisture content of said material after passage through said energy path and the press section and transmit a signal indicator of the water content of the web, respective controllers connected one to each slot to control the microwave energy output therefrom, and means applying to said controllers the signals emitted by said detector means to relate the output of each waveguide means to the water content measurement of a corresponding portion of the width of the material.
 3. A method of drying paper stock in the form of a traveling web containing water comprising selectively applying microwave energy in each of a plurality of zones extending transversely across the web to alter the viscosity of the water, then pressing the web to remove water therefrom, measuring the moisture content of each of said zones following water removal, and selectively controlling the application of the microwave energy in each of said zones in response to the measurement of the moisture content in each of said zones. 